International Journal of One Health, EISSN: 2455-8931 41
International Journal of One Health
Available at www.onehealthjournal.org/Vol.6/No.1/8.pdf
RESEARCH ARTICLE
Open Access
Microbial risk assessment of ready-to-eat fast foods from different
street-vended restaurants
Abdullah Al Momen Sabuj, Zobayda Farzana Haque, Md. Iftekhar Younus, Amrita Pondit, Nanda Barua,
Md. Golzar Hossain , Md. Alimul Islam and Sukumar Saha
Department of Microbiology and Hygiene, Faculty of Veterinary Science, Bangladesh Agricultural University,
Mymensingh-2202, Bangladesh.
Corresponding author: Sukumar Saha, e-mail: sukumar[email protected]
Co-authors: AAMS: [email protected], ZFH: [email protected],
MGH: [email protected], MAI: [email protected]
Received: 05-12-2019, Accepted: 09-03-2020, Published online: 03-05-2020
doi: www.doi.org/10.14202/IJOH.2020.41-48 How to cite this article: Sabuj AAM, Haque ZF, Younus MI, Pondit A, Barua N,
Hossain MG, Islam MA, Saha S (2020) Microbial risk assessment of ready-to-eat fast foods from different street-vended
restaurants, Int. J. One Health, 6(1): 41-48.
Abstract
Aim: Microbiological risk analysis of ready-to-eat fast foods for sale on the campus of Bangladesh Agricultural University
was undertaken to understand the contribution of such foods to foodborne disease.
Materials and Methods: From each of 10 randomly selected fast food outlets, a total of 120 samples of six food items
were collected to assess common microbial load. In parallel, vendors were asked about their food production and selling
practices, while consumers (n=200) were asked about their consumption of fast foods and whether they had experienced
symptoms of foodborne disease.
Results: Aerobic plate count (APC) varied from 6.92 to 7.24 log colony-forming unit (cfu)/g, Staphylococcus spp. 4.67 to
5.15 log cfu/g, Salmonella spp. 3.67 to 4.22 log cfu/g, and Escherichia coli 4.10 to 4.58 log cfu/g. Microbial risk assessment
of Staphylococcus spp., Salmonella spp., and E. coli for daily, weekly, or monthly consumption was estimated by Monte
Carlo simulation (10,000 iterations). The consumer survey showed 57% chance of being infected by ready-to-eat fast food
samples. The calculated mean annual risks of Staphylococcus spp., Salmonella spp., and E. coli infection were about 100%
in all cases.
Conclusion: Thus, the study revealed high risk of infection associated with the consumption of ready-to-eat fast foods.
Keywords: fast foods, microbial quality, microbial risk, Monte Carlo simulation.
Introduction
It has been estimated that foodborne disease
affects around 30 million individuals in Bangladesh
every year [1], and it has been postulated that “fast
food” (i.e., food that has been prepared for direct
human consumption without any need for further
processing or handling: [2]) contributes significantly
to this total. The consumption of fast food is increas-
ing worldwide, largely because it is generally cheap,
readily available, convenient, and fits well into an
urbanized lifestyle. Bangladesh has experienced rapid
societal changes, including urbanization, increased
female employment, longer working hours, education,
and other causes of absence from home, whose net
effect has been a rapid expansion in the number of fast
food premises. This increase in the fast food sector has
largely occurred without effective regulation of stan-
dards of food safety and hygiene [3], with the result
that, for most people, meals away from home mean
various forms of fast food that is prepared and sold at
small-scale roadside eateries which are usually unhy-
gienic. Such food is increasingly likely to represent
the main meal of the day.
There is a great variety of savory and sweet fast
foods available in Bangladesh [4], which are char-
acteristically made from reheated, precooked ingre-
dients, and are served in a packaged form for take-
out eating [5]. While most of the ingredients used
in manufacturing fast food are nutritious, all have
been shown to have the potential to harbor patho-
genic organisms, including Staphylococcus aureus,
Salmonella spp., Escherichia coli, Enterobacter spp.,
and Listeria monocytogenes, within the Bangladesh
fast food chain [6]. These bacteria are responsible
for causing foodborne diseases. A wide variety of
illnesses is caused by bacterial, viral, parasitic, and
chemical contamination that can occur in an unregu-
lated fast food market.
Ready-to-eat fast foods are, therefore, of great
significance in the epidemiology of foodborne disease
and are probably a major contributor to the increase
in foodborne illness that is taking place throughout
the world and turns into an alarming concern involv-
ing wide scope of infection caused by the harmful
Copyright: Sabuj, et al. This article is an open access article
distributed under the terms of the Creative Commons Attribution
4.0 International License (http://creativecommons.org/licenses/
by/4.0/), which permits unrestricted use, distribution, and
reproduction in any medium, provided you give appropriate credit
to the original author(s) and the source, provide a link to the
Creative Commons license, and indicate if changes were made.
The Creative Commons Public Domain Dedication waiver (http://
creativecommons.org/ publicdomain/zero/1.0/) applies to the data
made available in this article, unless otherwise stated.
International Journal of One Health, EISSN: 2455-8931 42
Available at www.onehealthjournal.org/Vol.6/No.1/8.pdf
microorganisms [7]. Moreover, there is a growing
concern for antimicrobial resistance in common
bacterial food contaminants. Ahmed et al. [3] have
recorded deaths in Bangladesh due to human infec-
tion with foodborne bacteria that were resistant to the
antibiotics that had been available for the treatment of
such infections.
Risk analysis is a useful food safety tool that helps
to identify foods or food ingredients that are actually
or potentially unsafe, or other hazardous materials
and/or practices, to reduce the rate of foodborne dis-
ease [8,9]. Risk analysis comprises three components:
Risk assessment, risk management, and risk commu-
nication. Risk assessment estimates adverse effects
on human health using pathophysiological and epide-
miological methods that relate to potentially hazard-
ous components [8]. More specifically, quantitative
microbial risk assessment (QMRA) evaluates the risks
that are related to the utilization of a specific food/
ingredient and provides an appraisal of the level of
illness that a particular pathogen can cause in a pop-
ulation who are exposed to contaminated food [10].
A preliminary microbial risk assessment of ready-
to-eat vegetable salads in Bangladesh Agricultural
University (BAU) was undertaken by Younus
et al. [11], with the key result that ~20% of students
who consumed such salads became infected with at
least one foodborne species of bacteria. However, that
study was undertaken with relatively small numbers
of participants, so more generalizable results need
to be developed. At present, around 10,000 students
are studying in BAU, most of whom are resident on
the campus. This densely-populated campus is ser-
viced by many food vendors and restaurants, who, as
with most urban fast food providers, are not subject
to stringent food safety and hygiene standards. Using
the campus as a model of a dense urban population,
and with regard to the results of Younus et al. [11] of
the likelihood of food contamination amongst its fast
food premises, the opportunity was taken to determine
the contribution of restaurant workers to the microbial
contamination of fast foods in different restaurants.
The present research was designed to, for fast
food premises on the BAU campus: (1) Determine
the presence and total viable bacterial load of com-
mon bacterial pathogens (with special emphasis on
Staphylococcus spp., Salmonella spp., and E. coli and
(2) undertake microbial risk assessment of fast food
items using Monte Carlo simulation, an exponential
predictive model.
Materials and Methods
Ethical approval and informed consent
No ethical approval was required; however,
during sample collection and survey, verbal permis-
sion was taken from restaurant vendors and consumers.
Selection of sampling sites
The study was carried out in and around the
campus of BAU, Mymensingh, Bangladesh, between
January 2017 and December 2017. There are nearly
50 fast food outlets that are distributed in seven major
locations around the BAU campus. Two outlets in each
of five of these locations were selected for sampling
based on the volume of sales and the density of outlets
in the location. The sampling program involved (i)
microbiological sampling of food that was for sale at
these outlets, (ii) a questionnaire-based study of food
handling practices, and (iii) verbal questioning of con-
sumers (purchasers) to evaluate the consumption pat-
tern of fast foods.
Microbiological samples
From each of the 10 selected fast food outlets,
at two different time points, six items (i.e., shingara,
samosa, piazu, puri, potato chop, and beguni) were
acquired as though being purchased and consumed
by consumers frequently. Each item (i.e., sample)
placed in a labeled sterile polyethylene container and
transported on ice to the laboratory. After weighing,
the sample was ground in a sterile mortar and pestle.
The sample was then mixed with nine volumes of
sterile distilled water in a sterile blending machine.
Thereafter, serial 10-fold dilutions (10−1-10−6) were
made from each sample.
Aliquots (0.1 mL) of each dilution of each
sample were inoculated onto microbiological culture
media: Nutrient agar, Mannitol salt (MS), Salmonella-
Shigella (SS), and eosin methylene blue (EMB) agar.
After 24 h of incubation at 37°C, colonies that were
golden-yellow, had a black center or metallic sheen
color colonies which were observed in MS, SS, and
EMB agar were identified as Staphylococcus spp.,
Salmonella spp., and E. coli, respectively. After that,
30-300 distinct colonies containing plates of each
specific media were counted and recorded as colo-
ny-forming unit (cfu)/g of fast food samples.
Evaluation of food handling practices
General observations were obtained from various
restaurants through observational questions to justify
the food handling practices conducted by restaurant
workers during sales. On each occasion, when food
samples were collected, the following observations
were made: (i) Types of fast food served in that
restaurant; (ii) the area where fast food is stored or
kept for sale; (iii) types of utensil used to serve food;
and (iv) practice of the food handlers during serving
the fast food. Furthermore, vendors were asked about
their food handling practices such as: (i) If they reheat
the food before sale; (ii) how they manage the leftover
food; and (iii) any training received on hygienic food
preparation and handling.
Verbal evaluation of fast food consumption patterns
A total of 200 questionnaires were distributed
to consumers comprising 100 males and 100 females
from each restaurant randomly, 10 male and 10
female consumers were asked to fill up the question-
naires. They were asked to answer the following
questions: (i) How old they were; (ii) how frequently
International Journal of One Health, EISSN: 2455-8931 43
Available at www.onehealthjournal.org/Vol.6/No.1/8.pdf
they consume fast food; (iii) from which source they
consume the fast food; (iv) why they eat fast food; (v)
if any disease experienced just after having the fast
food; and (vi) what type of disease or discomfort they
felt. The questionnaires were collected instantly after
they wrote the answers by themselves.
Microbial risk assessment
Microbial risk assessment comprises the four
steps of hazard identification, hazard characterization,
exposure assessment, and risk characterization [12].
The microbial risk associated with fast food han-
dling practices in the present study was conducted as
described by Amoah [13], as follows.
Hazard identification
Microbiological risk assessment starts with haz-
ard identification. These hazards were prospectively
identified as Staphylococcus spp., Salmonella spp.,
and E. coli contamination of fast food products. These
organisms were selected as the model QMRA organ-
isms as they are commonly present in food samples.
Dose-response assessment (hazard characterization)
Hazard characterization describes the adverse
health effects associated consumption of microor-
ganisms using dose-response relationships. An expo-
nential dose-response model [14] was used in this
study to predict the probability of Staphylococcus
spp., Salmonella spp., and E. coli infection, based on
microbial analysis of the selected organism. The equa-
tion used for determining the probability of infection
is as follows:
P(d)=1−e−rd
Where, P (d) is the probability of infection, d is
the dose (cfu) of microorganisms consumed per per-
son per day, and r is dimensionless infectivity con-
stant. The model parameter “r” used was 7.64×10−8for
Staphylococcus spp. [14], 3.97×10−6 for Salmonella
spp. [15], and 2.18×10−4for E. coli [16].
The final dose (d) of microorganisms consumed
by per person per serving was as the product of the
weight of food consumed and the quantity of organ-
isms present per gram of food (estimated as 50-70 g per
serving, based on serving size and consumers’ state-
ments of quantities that they consumed). Separate
risks were estimated according to each food item. The
final doses of Staphylococcus spp., Salmonella spp.,
and E. coli consumed per serving were inputted into
the mathematical model to obtain the probability of
infection per day.
Exposure assessment
This step of microbial risk assessment deals
with amount of food consumed and the frequency of
consumption of food for a specified period of time
to evaluate the consumer’s exposure to microorgan-
isms associated with particular food with a defined
period. Three exposure scenarios were estimated,
namely, frequent (daily), average (weekly), or occa-
sional (monthly) consumption of each fast food type,
as described by Amoah [13].
Risk characterization
This step integrates the previous three steps and
estimates the probability of infection in resulting from
exposure to hazards in every scenario. The annual
probability of infection for each scenario was calcu-
lated from the probability of infection and the number
of days of exposure within the year.
Pann=1−{1−P(d)}n
Where, n is the number of days of exposure
within the year.
Statistical analysis
Data were entered into SPSS 25.0 (IBM
Corporation, USA) for descriptive analysis. One-way
ANOVA was performed to compare difference among
the foods and statistical significance of difference
between means was tested at 95% confidence level
(p<0.05) by Tukey’s multiple test [17]. For each of the
exposure scenarios, a Monte Carlo simulation was run
using Microsoft Excel at risk software version 7.5.0
(Palisade Corporation) sampling 10,000 iterations to
determine the annual risk of infection for each expo-
sure scenario.
Results
Basic data
The average microbial load of all fast food items
is shown in Table-1. The highest aerobic plate count
(APC) was present in piazu samples (7.24 log cfu/g)
and the lowest in samosa samples (6.92 log cfu/g).
Staphylococcus spp. count was highest in puri sam-
ples (5.15 log cfu/g) and lowest in beguni sam-
ples (4.67 log cfu/g). The highest and lowest
E. coli counts were present in puri and piazu sam-
ples (4.58 log cfu/g vs. 4.10 log cfu/g), respectively.
The highest Salmonella spp. count (4.22 log cfu/g)
was present in samosa samples and the lowest
(3.67 log cfu/g) in shingara samples. The average
mean difference of APC, Staphylococcus spp., E. coli,
and Salmonella spp. among all ready-to-eat fast food
items was not statistically significant (p<0.05), but the
significant differences were observed in individual
food items among the selected restaurants.
All six fast food items were prepared by the
majority of the outlets. Handling practices utilized by
outlet workers are summarized in Table-2. Key results
were that food was stored in an open place in envi-
ronmental temperature (30-40°C) in 72% of outlets;
shared utensils were utilized to serve all of the different
types of food; workers did not use gloves for handling
food; leftover food was sold on the next day by all
outlets, and workers had not received any training on
hygienic food preparation and handling. On the other
hand, none of the outlets reheated food before the sale.
International Journal of One Health, EISSN: 2455-8931 44
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Fast food consumption data are summarized in
Table-3. The majority (53.5%) of respondents were
between 20 and 25 years of age, and most consumed
fast foods from on-campus outlets (51.5%) or uni-
versity canteens (43.5%). Fast foods were consumed
every day by 31% of the respondents, 42% once per
week, and 18.5% once per month. A total of 61% of
respondents had experienced disease that they asso-
ciated with eating fast foods. Of these, gastric reflux/
abdominal cramp, not associated with vomiting, was
reported by 31% of respondents.
Overall, there was 57% chance of being infected
by fast food items consumed by total consumers. Among
these, males had 49% chance and females had 67%
chance of being infected. Frequent consumers (daily)
had a higher chance (63%) of becoming infected than
other type of consumers. Respondents aged between 25
and 30 years of age had a higher chance (58%) of being
infected after consumption of fast food items in relation
to the respondents below 20 years of age (Table-4).
Risk analysis
Staphylococcus spp.
The dose-response assessment after Monte
Carlo simulation showed that the mean probability
of Staphylococcus spp. infection was 78% (90%
confidence interval [CI]: 4-234%) in puri samples
(highest) versus 24% (90% CI: 1-71%) in piazu sam-
ples (lowest). The mean annual risk of Staphylococcus
spp. infection was similar for all three consumption
frequencies (daily, weekly, and monthly) at 110%,
with minimum and maximum risk ranging from
100% to 213% (Table-5). The result demonstrates that
approximately 110 out of 100 consumers had a chance
of getting an infection with Staphylococcus spp. after
consumption of fast food, regardless of the frequency
of consumption.
Salmonella spp.
The probability of Salmonella spp. infection
highest at 99% (90% CI: 5-296%) in samosa and
potato samples versus other food items (for example,
the probability for shingara samples was 77% [90%
CI: 4-234%]). The annual risk of Salmonella spp.
infection did not differ between exposure frequen-
cies: The annual probability infection of Salmonella
spp. was 110% in frequent, average, and occasional
consumers, in whom the risk of infection varied from
100% to 226% (Table-6).
Table-1: Average microbial load of all ready-to-eat fast food samples.
Item (n=120) Microbial load (log cfu/g±SD)
APC Staphylococcus spp. Salmonella spp. Escherichia coli
Shingara (n=20) 7.12±0.42 4.69±0.61 3.67±0.10 4.28±0.56
Samosa (n=20) 6.92±0.45 4.77±0.70 4.22±0.64 4.52±0.39
Piazu (n=20) 7.24±0.09 4.71±0.33 - 4.10±0.54
Puri (n=20) 6.96±0.44 5.15±0.44 3.96±0.47 4.58±0.50
Potato chop (n=20) 7.03±0.59 4.84±0.03 4.07±0.55 4.35±0.54
Beguni (n=20) 6.94±0.50 4.67±0.62 4.04±0.46 4.20±0.40
According to the International Commission for Microbiological Specifications for Foods (ICMSF, 2002), acceptable
ranges of APC, Staphylococcus, and Escherichia coli are 106 cfu/g (6 log cfu/g), 104 cfu/g (4 log cfu/g), and
102 cfu/g (2 log cfu/g), respectively, and detection of any Salmonella spp. in a 25 g sample is unacceptable. APC=Aerobic
plate count, cfu=Colony-forming unit, SD=Standard deviation
Table-2: Fast food handling practice details.
Parameter Parameter Frequency (n=50) Percentage
Types of fast foods Shingara 50 100
Samosa 50 100
Piazu 44 88
Puri 50 100
Potato chop 34 68
Beguni 40 80
Fast food store or kept for sale Open place 36 72
Enclosed area 14 28
Utensil used to serve food Designated serving utensil 0 0
Shared utensil 50 100
Fast food served by food handlers Gloves protected hand 0 0
Bare hand 50 100
Reheat food before sale Yes 0 0
No 50 100
Management of leftover food Throw it away 0 0
Eat home 0 0
Sell it following day 50 100
Give to beggars 0 0
Any training received on hygienic food
preparation and handling
Yes 0 0
No 50 100
International Journal of One Health, EISSN: 2455-8931 45
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E. coli
The probability of E. coli infection was 100% in
all fast food items, although the CI was wide (90% CI:
5-300%). This organism also showed similar results of
annual risk of infection to the previous two organisms:
Consumers had 110% chance of becoming infected
with E. coli after consuming fast food items (Table-7).
Discussion
The substantive results of this study are,
first, that microbiological contamination of fast
food samples was widespread and at a high level.
All microbiological parameters (APC: 6.9-7.2 log
cfu/g, Staphylococcus spp. count: 4.7-5.2 log cfu/g,
Salmonella spp. count 3.7-4.2 log cfu/g, and E. coli
count: 4.1-4.6 log cfu/g) from all fast food samples
were well above the acceptable limits recognized by
the International Commission for Microbiological
Specifications for Foods [18]. Parallel studies under-
taken in other developing countries have shown
similar results. Akusu et al. [19], who studied dif-
ferent ready-to-eat fast food samples in Rivers State,
Table-3: Fast food consumption details.
Parameter Consumer Distribution of respondents Percentage
Male (n=100) Female (n=100) Total (n=200)
Age Below 20 27 10 37 18.5
20-25 40 67 107 53.5
25-30 33 23 56 28.0
Fast food consumption
frequency
Every day 37 25 62 31.0
Once in week 36 48 84 42.0
Once in month 17 20 37 18.5
Unspecified 10 7 17 8.5
Source from which fast
food is consumed
Home 3 3 6 3.0
Restaurants 57 46 103 51.5
Canteen 37 50 87 43.5
Others 3 1 4 2.0
Reason for eating fast
food
Health benefits 0 1 1 0.5
Taste 85 71 156 78.0
Esthetic appeal 9 12 21 10.5
Social interaction 4 8 12 6.0
Others 1 9 10 5.0
Disease experienced Yes 55 67 122 61.0
No 45 33 78 39.0
Types of diseases Acidity 24 38 62 31.0
Vomiting 1 9 10 5.0
Abdominal discomfort 14 12 26 13.0
Others 16 8 24 12.0
None 45 33 78 39.0
Table-4: Risk assessment of consumers according to different parameter.
Parameter Consumers Number of consumers (n) Case findings (d) Risk (d/n) Percentage
Sex Male 57 28 0.49 49
Female 46 31 0.67 67
Type of consumers Frequent 32 20 0.63 63
Average 38 22 0.58 58
Occasional 26 13 0.50 50
Unspecified 7 4 0.57 57
Age <20 25 11 0.44 44
20-25 53 30 0.57 57
25-30 25 18 0.72 72
Table-5: Risk assessment of Staphylococcus spp. in all ready-to-eat fast food items.
Ready-to-eat
fast food
items
Mean dose of
organisms per
serving (cfu)
Mean probability
of infection
(90% CI)
Mean annual risk of infection (90% CI)
Frequent
consumer (daily)
Average
consumer (weekly)
Occasional
consumer (monthly)
Shingara 7.73×10644 (2-131) 110 (100-206) 110 (100-193) 110 (100-200)
Samosa 1.15×10758 (3-174) 110 (100-199) 110 (100-193) 110 (100-197)
Piazu 3.60×10624 (1-71) 110 (100-207) 110 (100-187) 110 (100-200)
Puri 2.0×10778 (4-234) 110 (100-192) 110 (100-211) 110 (100-204)
Potato chop 5.98×10637 (1-110) 110 (100-193) 110 (100-192) 110 (100-206)
Beguni 6.01×10637 (1-110) 110 (100-195) 110 (100-213) 110 (100-187)
cfu=Colony-forming unit, CI=Confidence interval
6
7
8
1
/
8
100%
